Leak detector

ABSTRACT

A leak detector includes an off-center mounted metering pin cooperating with a single cross-hole in a poppet valve to accommodate adjustment of the flow rate past the metering pin by rotating the poppet valve about its longitudinal axis. A flow director, cooperating with the poppet valve, directs all flow into the leak detector directly into the line during initial flow into the leak detector. A piston, responsive to line pressure, is sized smaller in diameter than the poppet valve to cause the line pressure to increase rapidly and significantly during the leak sense mode and which size permits reduction in size and weight of the leak detector.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is based upon and includes a disclosurecontained in a provisional application entitled “LEAK DETECTOR” filedFeb. 22, 2000, and assigned Ser. No. 60/______, (our docket number3410-P-19), which application is assigned to the present assignee.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to leak detectors and, moreparticularly, to a leak detector which increases the line pressure to ashigh a value as possible during the metering cycle of the leak detector.

[0004] 2. Description of Related Art

[0005] Gasoline dispensers used at automotive service stations dispensegasoline from an underground tank through a nozzle placed in the filltube of an automobile gas tank. The underground tank includes a pumpactuated by a user upon manipulation of a lever at the time of liftingthe nozzle from its stored position on the gasoline dispenser.Downstream of the pump is a conventional leak detector, which may be ofa piston or diaphragm type. For example, a diaphragm leak detector longused since 1976 is known as a Red Jacket Two-Second Model No. 116-017Leak Detector; a similar unit has been used since 1959. These units aremanufactured by the Marley Pump Company.

[0006] The gasoline line downstream of the leak detector may have a leakwhich creates an environmental hazard to the adjacent underground and asevere safety hazard to personnel. Such leaks are difficult to detectfrom the surface of the ground and the leak detectors serve the functionof precluding delivery of gasoline through the delivery line if a leakof greater than a predetermined rate is present. Trapped air in thedelivery line usually does not present a safety hazard but it may havethe effect of extending the leak sensing function of a leak detector tothe irritation of a user attempting to dispense gasoline. Changes inenvironmental temperatures may expand or contract the gasoline (product)within the delivery line which will vary the pressure in the deliveryline and have an effect upon the operation of the leak detector. Uponclosing of the dispensing nozzle, a pressure wave rebounds from thedispensing nozzle upstream through the delivery line to the leakdetector. The pressure wave, often referred to as hydraulic hammer,subjects the leak detector to a potential for severe damage of criticalparts, including rupture of the diaphragm in a diaphragm type leakdetector. Such damage may be undetected for an extended period of time.If leaks in the delivery line are present or result from the damagingeffects of hydraulic hammer, the damaged leak detector would beincapable of serving the function of detecting such leaks. The resultingenvironmental and safety hazards would continue unchecked. Hydraulichammer also causes the leak detector to open prematurely because of theresulting excess pressure downstream of the leak detector. Just turningon the pump, without actuating the nozzle, may cause hydraulic hammer toa detrimental extent.

[0007] A mechanical line leak detector is a pressure sensitive valvethat incorporates a built-in metering device. The leak detector isplaced into the line between the pump in fluid communication with anabove-ground or an underground gasoline tank (storage tank) and thedispenser at the outflow end of the gasoline (product) delivery line insuch a manner that the pump is on the upstream side of the leak detectorand the delivery line and dispenser are on the downstream side. Mostmodern pumps for storage tanks have a leak detector port built in forthis purpose. Simply stated, when the pump at the storage tank isenergized, the leak detector will go to a slow-flow position (poppetvalve completely down) for line pressurization. When sufficient linepressure has been achieved, the poppet valve will move upward to ametering position (cross-holes in the poppet valve aligned with a pinhead). At this point, a predetermined amount of product is metered intothe line downstream of the leak detector. If there is a leak in the linethat is as great as or greater than the predetermined metered flowentering the line, the pressure in the line will not increase and theleak detector will not open for full product flow. If there is no leak,line pressure will continue to increase and the poppet valve will moveto its full open position allowing full flow of product into the line.The functions recited above are true of all mechanical leak detectorsknown to date.

[0008] To have a trouble free leak detector, numerous problems must beaddressed. These include: hydraulic hammer created in the line which maycause the leak detector to open prematurely; loss of line pressure dueto a faulty check valve at the pump drawing product from the storagetank; lack of repeatedability in the metering position of the leakdetector due to small tolerances that may vary over time; leak sensingor metering pressure in the line being too low to achieve the greatestsensitivity and speed of operation; thermal contraction in the line;high frequency pressure surge from the storage tank pump causingpremature opening of the leak detector; premature closing of the leakdetector during a fueling operation due to reduced pressure; and,excessive size and weight of prior art leak detectors renderinginstallation, maintenance and removal more of a problem than necessary.

SUMMARY OF THE INVENTION

[0009] A bore in the basket of a leak detector is drilled off center andsupports a pin. Flow through a single side cross-hole of the poppetvalve in proximity to the pin is adjustable by rotating the poppet valveabout the pin to vary the clearance between the pin and the outlet ofthe single cross-hole. A clutch mechanism precludes movement of thepoppet valve relative to the pin during normal use to maintain theclearance set except upon deliberate rotational adjustment thereof. Thepoppet valve, serving as one of two pistons, is attached by a shaft to asecond piston. By maintaining the effective diameter of the secondpiston slightly smaller than that of the effective diameter of thepiston represented by the poppet valve, significantly greater linepressure acting upon the second piston is required to overcome thepressure exerted by the pump at the storage tank upon the poppet valve.This results in significantly greater line pressure during the meteringcycle and thereby accuracy and effectiveness is significantly improved.Such higher line pressure during the metering cycle also effectivelyreduces the effects of thermal contraction and line resiliency (air,line stretch, etc.,) during the metering cycle. Further, the initialsurge of product upon actuation of the pump at the storage tank will notact upon the leak detector to cause the leak detector to step through tofull flow prematurely as the initial flow from the pump is through aby-pass in the leak detector and directly into the line. With thereduced size second piston, leak detectors incorporating the presentinvention may be on the order of one-third of the weight and one-half ofthe size of prior art leak detectors.

[0010] It is therefore a primary object of the present invention toprovide a leak detector which rapidly pressurizes a line to a highpressure.

[0011] Another object of the present invention is to provide a leakdetector having an adjustable and maintainable flow rate through thepoppet valve at each of the three modes of operation.

[0012] Yet another object of the present invention is to provide a leakdetector having an adjustable flow rate past a metering pin by rotatingthe poppet valve about the pin.

[0013] Yet another object of the present invention is to provide aparked position for the leak detector which directs outflow from astorage tank directly into the line upon actuation of a pump.

[0014] Still another object of the present invention is to prevent aninitial surge of product flow from causing a leak detector to begin itsstepping functions.

[0015] A further object of the present invention is to provide apressure balance between the pressure acting upon a poppet valve and asecondary piston by use of a relatively weak spring urging downwardmovement of the second piston.

[0016] A yet further object of the present invention is to provide aleak detector of small size and low weight;

[0017] A still further object of the present invention is to provide amethod for stepping a leak detector through the steps of parkedposition, line fill, leak sense and full flow.

[0018] These and other objects of the present invention will becomeapparent to those skilled in the art as the description thereofproceeds.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be described with greater specificityand clarity with reference to the following drawings, in which:

[0020]FIG. 1 is a schematic of the flow paths through a conventionalprior art leak detector;

[0021]FIGS. 1A, 1B, 1C, 1D and 1E illustrate the discreet elements shownin FIG. 1;

[0022]FIG. 2 illustrates the initial flow through a prior art leakdetector;

[0023]FIG. 3 illustrates the initial flow through the leak detectordescribed herein;

[0024]FIG. 4 illustrates an exploded view of the components of thepresent detector;

[0025]FIG. 5 illustrates an exploded view similar to FIG. 4 and alsoshowing a check valve and its components;

[0026]FIG. 6 illustrates a cross-sectional view of the leak detector;

[0027]FIG. 7 illustrates a schematic of the flow paths through presentthe leak detector to show the differences in the flow path from that ofthe prior art shown in FIG. 1;

[0028]FIGS. 7A, 7B, 7C, 7D, and 7E illustrates the discreet elementsshown in FIG. 7 of the present leak detector and illustrate thedifferences with the corresponding components of the prior art shown inFIGS. 1A through 1E;

[0029]FIGS. 8A and 8B show cross-sectional views of the components ofthe leak detector in its parked position;

[0030]FIGS. 9A and 9B show cross-sectional view of the components of theleak detector in the reset position;

[0031]FIGS. 10A and 10B show cross-sectional view of the components ofthe leak detector in the leak sense position;

[0032]FIGS. 11A and 11B show cross-sectional view of the components ofthe leak detector in the full flow position;

[0033]FIG. 12 is a bottom view of the flow director particularly shownin FIGS. 4 and 5;

[0034]FIG. 12A is a cross-sectional view taken along lines 12A-12A,shown in FIG. 12;

[0035]FIG. 12B is a cross-sectional view taken along lines 12B-12B,shown in FIG. 12;

[0036]FIG. 12C is a side view of the flow director; and

[0037]FIG. 12D is a top view of the flow director.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0038] Referring to FIG. 1, there is illustrated a schematic of theoperation of a leak detector 10 of a type that has been manufactured fora period of years; this type of leak detector is an industry standardand is used in conjunction with tens of thousands of gasoline storagetanks and delivery systems at retail service stations. The followingdiscussion will refer jointly to FIGS. 1 and 1A to 1E. Inflow 12 resultsfrom actuation of a pump associated with an underground (above-ground)gasoline (product) storage tank. The inflow enters a channel 14 and intoa poppet valve 16. The position of pin 18 within the poppet valvepermits a limited rate outflow 20 into a line conveying the product tothe gasoline dispenser at a service station. As the line fills, returnflows 22, 24 enter leak detector 10 flowing upwardly through channels26, 28 in the poppet valve. These return flows are channeled through acollar 30 and into a hollow shaft 32 threadedly connected to the collarand poppet valve 16. Flow 34 through the shaft is discharged throughchannels 36, 38 into a cylinder beneath piston 40 attached to shaft 32.The product collecting within the cylinder will cause piston 40 to rise.The raising of the piston will result in commensurate displacement ofpoppet valve 16 relative to pin 18 and further flow 20 will occur at adifferent rate to determine the presence of a leak. If no leak is found,further return flow 22, 24, will cause piston 40 to rise further untilpoppet valve 16 clears pin 18 resulting in full flow of product into theline.

[0039] As set forth above, hydraulic hammer in the line will affect theforce of return flows 22, 24 and may result in false indications. Suchfalse indications may include the raising of piston 40 to result in fullflow without there having been an opportunity to sense for leaks in thesystem. Furthermore, the hydraulic hammer may cause damage to thecomponents of the leak detector and compromise its integrity.

[0040] Referring to FIG. 2, there is illustrated a further problemattendant prior art leak detectors. Upon actuation of a pump to pumpproduct from an underground gasoline tank, there exists a high frequencypump surge in inflow 12. This inflow will flow past pin 18 in poppetvalve 16 through shaft 32 and into the cylinder below piston 40.Simultaneously, a certain amount of product will flow past pin 18 inpoppet valve 16 as outflow 20 into the line. A return flow 24 from theline will flow through the poppet valve channels 26, 28, through shaft32 and into the cylinder adjacent piston 40. This surge of pressureacting upon piston 40 may cause a premature upward movement of piston40, attached shaft 32 and poppet valve 16 relative to pin 18. The changein physical relationship between the pin and the poppet valve willaffect the flow rate into the line and may cause premature stepping ofthe leak detector from step 1 (filling of the line) to step 3 (fullflow) without conducting step 2 (leak detection).

[0041] In the present invention shown in FIG. 3, a flow director 50 ispositioned with respect to and retained by poppet valve 16. The flowdirector precludes flow 12 of product from the pump into shaft 32 and tothe cylinder adjacent piston 40. Instead, inflow 12 flows past pin 18 inpoppet valve 16 to outflow 20. Additionally, inflow 12 flows past pin 18upwardly adjacent flow director 50 and is channeled thereby into channel28 in the poppet valve to be redirected downwardly to the line, asdepicted by flow 20A. By initially directing all of the product into theline, the line will fill relatively quickly. Any pressure surge will betransmitted into the line and in fact enhance filling of the line to theextent necessary. After the line is filled, return flow 24 will occurand such flow will flow upwardly through shaft 32 into the cylinderbeneath piston 40. Thereby, the present invention eliminates falseactuation due to a high frequency pump surge as all of initial inflow 12from the pump is directed into the line.

[0042] Referring to FIG. 4, there is illustrated an exploded view of thecomponents of present leak detector 60. A conventional basket 62supports pin 18 in a counterbore, which counterbore is slightlyoff-center. A poppet valve 16 penetrably receives pin 18 is passageway74. A flow director 64 is at least partially disposed within poppetvalve 16 (see FIG. 6). The engagement therebetween may be a press fit toensure alignment between passageway 66 through the poppet valve withpassageway 68 in the flow director and alignment of elongated cavity 70with passageways 72, 74 in the poppet valve to cause return flow throughpassageway 72 of all flow upwardly through passageway 74. The flowdirector may be mechanically keyed to or otherwise attached to thepoppet valve to ensure that there is not relative mechanical movementtherebetween. Guide 76 includes a depression 78 for receiving flowdirector 64 and the upper end of the poppet valve. Shaft 32 is inthreaded engagement with flow director 64. A guide 80 includes ashoulder 81 bearing against an annular flange 128 (see FIG. 6) disposedwithin casing 82 to limit upward movement of the guide. A spring 84bears against shoulder 81 of the guide to urge downward movement ofguide 76 and commensurate movement of shaft 32. A piston 40 is securedto shaft 32 and retained thereon by a nut 86. Piston 40 is disposedwithin a cylinder 120 (see FIG. 6) in casing 82. Basket 62 includesthreads for threadedly engaging the lower end of casing 82, and anoff-center counterbore 63 for supporting pin 18. A housing 90 containscasing 82 and the structures disposed therein. A fitting 92 is disposedat the upper end of housing 90 for fluid communication with the spaceattendant the top side of piston 40. Various O-rings and seals, asillustrated, are employed to serve various sealing functions. Asillustrated, decals, serial number plates and the like may be disposedupon the housing.

[0043] Referring to FIG. 5, there is illustrated a leak detector likethat described in FIG. 4. However, a check valve assembly 96 extendsinto the line from basket 62. The purpose of the check valve assembly isthat of protecting the components of the leak detector against hydraulichammer and other sudden pressure surges within the line that may occurduring normal and abnormal operation. In essence, the check valveassembly includes a seal 98 and a piston 100 slidably mounted upon ashaft 102 extending downstream from basket 62. A spring 104 is retainedin place by a screw 106 in threaded engagement with internally threadedshaft 102 and a washer 107 against which the spring bears. The other endof the spring bears against a flange 108 of piston 100. When the outflowpressure at basket 62 to is greater than line pressure, the outflow willcause seal 98 and piston 100 to translate against spring 104 along shaft102 and permit flow into the line. When the line pressure is greaterthan the pressure within the basket, spring 104, acting against piston100, will cause translation of piston 100 and seal 98 will seal theoutlet of basket 62. A relief valve 110, including a correspondingaperture 112 in seal 98, will accommodate controlled flow through thecheck valve. The remaining elements illustrated in FIG. 5 correspondwith those discussed above with respect to FIG. 4.

[0044] Referring to FIG. 6, there is illustrated a cross-sectional viewof leak detector 60 in its assembled state. Certain features not evidentfrom the exploded view shown in FIGS. 4 and 5 will be described. Pin 114is lodged in casing 62 and extends into slot 116 extendinglongitudinally along guide 76 to preclude rotation of the guide. Theearlier discussed annular flange 118 extending regularly inwardly withincasing 62 serves as a shoulder against which guide 80 bears and whichlimits the upward movement of the guide. As is evident in FIG. 6, upwardmovement of poppet valve 16 will result in upward movement of shaft 32which movement is restrained by compression of spring 84. Flow intocylinder 120 beneath piston 40 and within casing 62 occurs from thepoppet valve through passageway 122 and lateral channels 124, 126 in theshaft. A seal 128 about the base of the poppet valve precludes flow ofproduct between the poppet valve and lower cylindrical surface 130 ofcasing 62. Basket 62 is essentially flush with the bottom of the casing,as illustrated. As will be described in further detail below, piston 40is secured to shaft 32 by a nut 132.

[0045] Referring jointly to FIGS. 7, 7A, 7B, 7C, 7D and 7E, thedifference in flow paths upon initial actuation of the pump to pumpproduct from a storage tank into leak detector 60 will be described. Inthis discussion it may be well to also refer to FIGS. 1, 1A, 1B, 1C, 1D,and 1E which illustrate the commensurate flow path in a prior art leakdetector. Inflow 140 from the pump enters a channel 142 in poppet valve144. As a result of the off-center position of pin 146 relative topassageway 148 in poppet valve 144, and outflow 150 of product into theline will result through the passageway past the pin. A further flow ofproduct from inflow 140 will flow upwardly into an elongated cavity 70in flow director 64. Outflow 152 will flow from the cavity and through apassageway 154 in the poppet valve. No inflow of product will find itsway into passageway 122 of hollow shaft 32. As the line becomes full, areturn flow 160 will flow into passageway 162 of the poppet valve. Thispassageway is in fluid communication with passageways 164, 166 in flowdirector 64 to direct such return flow into opening 168 at the bottom ofhollow shaft 32. The return flow will flow upwardly through the shaftand be exhausted through passageway 124, 126 into the cylinder beneathpiston 80. Thereby, flow director 64 precludes an initial pressure surgefrom causing any flow of product through the shaft and into the cylinderbeneath piston 80.

[0046] Referring jointly to FIGS. 8A and 8B, the “parked” position forleak detector 60 will be described. When the pressure within the linefrom the leak detector to a dispensing pump drops to approximately 5psi, the pressure within cylinder 120 acting upon piston 80 isinsufficient to overcome the spring force of spring 84. Consequently,poppet valve 16 will translate downwardly to its “parked” position, asillustrated. In this position, the bottom of the poppet valve cross-hole170 is essentially aligned with the top of pin 18. In this parkedposition, leak detector 60 is in the initial position ready to receivean inflow of product from the pump associated with the supply of product(tank). For reference purpose, a receiver 172 at the inlet end of theline to the dispensing pump is shown and housing 90 is in threadedengagement therewith.

[0047] Upon actuation of the pump, the initial pressure surge will causeflow of product into the poppet valve and out through channel 154. Asthe pressure and product flow continue, pressure acting upon seal 128sealing the perimeter of the lower end of poppet valve 16 will urgedownward movement of the poppet valve to the position shown in FIGS. 9Aand 9B. In this position, cross-hole 170 of the poppet valve willessentially straddle the bottom edge of head 174 of pin 18. This willresult in flow of product through the cross-hole and upwardly past thehead of the pin into cavity 70 of flow director 64 and thereafterdownwardly through the poppet valve to exit through the passageway 154.Simultaneously, flow of product from the outlet of the cross-hole willflow downwardly adjacent shaft 176 of pin 18 and into passageway 154.The downward movement of poppet valve 16 results in commensuratetranslation of shaft 32 and downward movement of piston 80. As all ofthe product inflowing into the poppet valve is directed downstream intothe line, the line will quickly fill. After fill, return flow will flowthrough the poppet valve, the flow director and the shaft into cylinder120 beneath piston 80. In this position of the poppet valve, the flowrate is approximately one and a half gallons per minute (1-½gal./min),which flow rate is an industry standard. This is the line fill mode.

[0048] As the line pressure reaches approximately 21 psi, the pressurewithin cylinder 120 acting upon piston 80 will overcome the spring forceexerted by spring 84 and the piston will rise. A commensuraterepositioning of poppet valve 16 will occur. Raising the poppet valvewill reposition cross-hole 170 in alignment with the side of head 174 ofpin 18, as shown in FIGS. 10A and 10B. Outflows 152 and 154 willcontinue but at a reduced combined rate of two gallons per hour (2gal./hr). This is the leak sense mode. In the event that there is a leakof 2 gal./hr or more downstream of leak detector 60, there will be nofurther pressure buildup within the cylinder 120. Without furtherrepositioning of piston 80 as a result of an increase in pressure withincylinder 120, the flow rate through the leak detector will be limited totwo gallons per hour.

[0049] In the event there is no leak in the line or there is a leak lessthan two gallons per hour, the pressure within cylinder 120 willcontinue to increase and the volume will increase resulting in upwardmovement of piston 80, as shown in FIG. 11A. The resulting upwardmovement of piston 80 will produce a commensurate movement of poppetvalve 16, as shown in FIG. 11B. At approximately 24 psi within cylinder120, the poppet valve will have been raised sufficiently to clear pin18. Upon such clearance, the full pressure exerted by the pump at thestorage tank will be translated into a commensurate pressure withincylinder 120, as depicted by flow path 180. Moreover, the poppet valvewill no longer restrain outflow of product through basket 62 into theline.

[0050] Referring jointly to FIG. 12 and FIGS. 12A, 12B, 12C, 12D,details of flow director 64 will be described. The flow directorincludes a threaded cavity 190 for threadedly engaging the lower end ofshaft 32. A passageway 192 in combination with passageway 194constitute, in essence, a single passageway to accommodate flow throughthe flow director from the poppet valve into passageway 122 within shaft32. A cavity 70 is formed in the bottom surface of the flow director toredirect flow upwardly from about the metering pin in the poppet valveinto downward flow through a passageway in the poppet valve.

[0051] The poppet valve of prior art leak detectors included a pair ofopposed cross-holes for cooperating with the pin extending from thebasket for limiting flow through the poppet valve as a function of themode of a leak detector. Such mechanical arrangement rendered it verydifficult to adjust in the field the flow rates through the cross-holesduring line fill and leak sense modes. Essentially, any adjustments hadto be made by replacing the metering pin with a metering pin ofdifferent size. Field adjustments of this type were expensive and timeconsuming. Therefore, workman often replaced the complete leak detector.By using a single cross-hole and having, the pin off-center with respectto its corresponding passageway, its proximity to the outlet of thecross-hole could be adjusted by simply rotating the poppet valve toplace the outlet of the cross-hole laterally closer or further away fromthe head of the pin.

[0052] Referring to FIG. 6, there is shown a nut 132 disposed at the topof piston 40. By rotating this nut, in a clockwise direction, the shaft,the flow director and the poppet valve housing would rotate acommensurate amount relative to the non-rotatable fixed off-centermounted pin. Thereby, the lateral distance between the head of the pinand the cross-hole could be easily adjusted in the field. Pin 114,engaging slot 116 of guide 76 precludes rotation of the guide. Bycreating a close high friction press fit between cavity 78 in the guideand the part of the poppet valve disposed therein, a clutch is createdto prevent unwanted rotation of the poppet valve about its longitudinalaxis except upon deliberate rotation of shaft 32 via its threadedlyattached nut 132. The flow director and the poppet valve must bemechanically attached or keyed with one another to prevent relativerotation therebetween about their common longitudinal axis.

[0053] The poppet valve attached to one end of shaft 32 is in the natureof a piston translatable along a cylindrical cavity and downwardmovement is urged by fluid pressure exerted by the upstream pump. Piston40, disposed at the opposite end of the shaft is urged upwardly bypressure in cylinder 120 as a result of flow of product from the linedownstream of the poppet valve. The relative effective area of thepoppet valve is approximately 40% of the effective area of the piston.For example, the piston may be about 1 inch in diameter and the poppetvalve may be about 1-¼ inches in diameter. In order to achieve upwardmovement of shaft 32 and ultimate displacement of the poppet valve fromthe metering pin, the upward force exerted upon piston 40 by thepressure in cylinder 120 must be greater than the downward force exertedupon the poppet valve by the pressure of the pump. If the force actingon the piston is slightly more than the force acting upon the poppetvalve, significant line pressure must be present in order to result inupward translation of shaft 32. Such requirement for significant linepressure enhances the likelihood of rapidly detecting a leak.

[0054] Because prior art devices embodied a piston of significantlylarger size diameter than that of the poppet valve, a much lesser lineof pressure was required to result in displacement of the poppet valvefrom the metering pin. Thus, a much lower pressure was present during ametering mode of the leak detector. Furthermore, resetting the leakdetector was more difficult with a significantly larger diameter pistonwhen there was any head pressure present in the line and required a muchstronger spring to urge downward movement of the poppet valve.

[0055] The reduced required size of the piston in the present inventionpermits a reduced diameter casing and housing, which has the furtherbenefit of significant weight reduction.

[0056] While the invention has been described with reference to severalparticular embodiments thereof, those skilled in the art will be able tomake the various modifications to the described embodiments of theinvention without departing from the true spirit and scope of theinvention. It is intended that all combinations of elements and stepswhich perform substantially the same function in substantially the sameway to achieve the same result are within the scope of the invention.

I claim:
 1. A leak detector for use with a pump pumping product from astorage tank through said leak detector into a line having an outlet ata product dispenser, said leak detector comprising in combination; a) apoppet valve having a passageway and a single cross-hole in fluidcommunication with said passageway; b) a metering pin cooperating withsaid poppet valve to meter flow through said cross-hole into saidpassageway of said poppet valve as a function of the position of saidpoppet valve relative to said pin, said pin being mounted off-center ofsaid passageway; c) means for rotating said poppet valve to adjust thespacing between said pin and said cross-hole as a function of therotational position of said poppet valve; d) a flow director fordirecting a flow of product into the line upon initial actuation of thepump; e) a piston having an effective area less than the effective areaof said poppet valve, said piston being axially translatable in responseto return flow of product from the line to displace said poppet valverelative to said pin during flow of product into the line; and f) aspring for restraining displacement of said poppet valve in response totranslation of said piston.
 2. A leak detector as set forth in claim 1including a check valve for preventing flow of product into said leakdetector from the line when the line pressure of the product is greaterthan the pressure of the product exerted upon said leak detector by thepump.
 3. A leak detector as set forth in claim 1 wherein said poppetvalve includes a further passageway for directing flow of product fromthe pump into the line and wherein said flow director directs flow ofproduct from about said pin within said passageway into said furtherpassageway.
 4. A leak detector as set forth in claim 3 wherein said flowdirector includes a yet further passageway for directing product fromthe line into a cylinder associated with said piston.
 5. A leak detectoras set forth in claim 1 including a hollow shaft interconnecting saidpoppet valve with said piston.
 6. A leak detector as set forth in claim1 including means for rotating said shaft to rotationally repositionsaid poppet valve relative to said pin to adjust the spacing betweensaid pin and said cross-hole.
 7. A method for detecting a leak ofproduct downstream of a leak detector in fluid communication with a pumpfor pumping the product from a tank, said method comprising the stepsof: a) directing all of the initial flow of product from the pumpdirectly into the line; b) metering the flow rate of product into theline at a first rate with a poppet valve having a single cross-holedirecting the product to and about a metering pin during a line fillmode; c) displacing the poppet valve relative to the pin to establish asecond rate of product flow into the line during a leak sense mode; d)further displacing the poppet valve to prevent the metering pin fromrestricting flow through the leak detector during a full flow mode; ande) adjusting the pin controlled flow rate by rotating the poppet valverelative to the pin to adjust the distance between the outlet of thecross-hole and the metering pin.
 8. A method as set forth in claim 7including a shaft attached to the poppet valve and wherein said step ofadjusting is performed by rotating the shaft.
 9. A method as set forthin claim 7 including the step of controlling the displacement of thepoppet valve with a piston having an effective diameter less than theeffective diameter of the poppet valve, the piston being positionallyresponsive to the difference between the pressure extended upon thepoppet valve by product flowing from the pump and the pressure of theproduct in the line translated to the piston which pressure differenceis in excess of the force exerted by a spring restraining movement ofthe poppet valve.
 10. A method for adjusting a leak detector having apoppet valve and an associated pin for metering flow of product throughthe poppet valve, the poppet valve including a single cross-hole fordirecting flow of product to be metered into a central passageway, theleak detector including a basket for supporting the metering pinoff-center within the passageway of the poppet valve, said methodincluding the steps of: a) rotating the poppet valve to set the spacebetween the outlet of the cross-hole and the metering pin; and b)restraining rotational movement of the poppet valve with a clutch.
 11. Aleak detector for use with a pump pumping product from a storage tankthrough said leak detector into a line having an outlet at a productdispenser, said leak detector comprising in combination: a) a poppetvalve having a passageway and a single cross-hole in fluid communicationwith said passageway; b) a metering pin cooperating with said poppetvalve to meter flow through said cross-hole of said poppet valve as afunction of the spacing between said cross-hole and said metering pin,said pin being mounted off-center of said passageway; and c) means forrotating said poppet valve to adjust the spacing between said cross-holeand said pin as a function of the rotational position of said poppetvalve.
 12. A leak detector as set forth in claim 11 including a checkvalve for preventing flow of product into said leak detector from theline when the line pressure of the product is greater than the pressureof the product exerted upon said leak detector by the pump.
 13. A leakdetector as set forth in claim 11 including a piston having a diameterless than the diameter of said poppet valve, said piston being axiallytranslatable in response to return flow of product from the line todisplace said poppet valve relative to said pin during flow of productinto the line.
 14. A leak detector as set forth in claim 13 including ashaft interconnecting said poppet valve with said piston.
 15. A leakdetector as set forth in claim 14 including means for rotating saidshaft to rotationally reposition said poppet valve relative to said pinto adjust the spacing between said pin and said cross-hole.
 16. A leakdetector for use with a pump pumping product from a storage tank throughsaid leak detector into a line having an outlet at a product dispenser,said leak detector comprising in combination: a) a poppet valve having apassageway and a further passageway; b) a metering pin cooperating withsaid poppet valve to meter flow through said passageway; and c) a flowdirector for directing all flow of product into the line through saidfurther passageway upon initial actuation of the pump.
 17. A leakdetector as set forth in claim 16 including a check valve for preventingflow of product into said leak detector from the line when the linepressure of the product is greater than the pressure of the productexerted upon said leak detector by the pump.
 18. A leak detector as setforth in claim 16 wherein said flow director directs flow of productfrom about said pin within said passageway into said further passageway.19. A leak detector as set forth in claim 16 including a pistoninterconnected with said poppet valve, said piston having a diameterless than the diameter of said poppet valve, said piston being axiallytranslatable in response to return flow of product from the line todisplace said poppet valve relative to said pin during flow of productinto the line.
 20. A leak detector as set forth in claim 19 including ahollow shaft interconnecting said poppet valve with said piston.
 21. Aleak detector as set forth in claim 20 including means for rotating saidshaft to rotationally reposition said poppet valve relative to said pinand to adjust the spacing between said pin and said cross-hole.